This invention relates to container closures, and more particularly to closure devices for prohibiting access to container contents by children while permitting such access by adults.
Many useful products, such as medicines and household cleaners, cannot be made inherently safe from improper use by children and others who may be unable to appreciate the danger presented by the product. A common problem with the distribution of such products is prohibiting access to the product by children while permitting access by adults. Accordingly, a variety of child resistant closures have been developed for use with common product containers. Such closures generally include an obstacle which is intended to be relatively difficult for a child to avoid but which can be easily overcome by an adult.
U.S. Pat. No. 3,845,872 discloses a child resistant closure plug for use with a container having a substantially cylindrical mouth. The closure has a cylindrical body portion which extends into the mouth of the container, and a disk-shaped cover portion which is attached to the body. An undercut groove or notch is provided on the outside surface of the cylindrical body portion where it meets the cover. A corresponding lip is provided on the inside wall of the container mouth to engage the undercut groove. The groove and lip thus cooperate to retain the closure in the container, and substantial force is required to overcome the cooperation of these elements to remove the closure.
A hinged flap or tab is provided in the cover to serve as a handle or lever f or removing the closure from the container. A recess is provided in the cover in which the tab may be retained in a closed position when it is not being used to remove the closure from the container. When the tab is in its closed position, its upper surface is substantially flush with the upper surface of the cover. The tab and recess have cooperative means to release the tab when downward pressure is applied at a predetermined position.
Because it is extremely difficult to remove the closure from the container without using the tab handle, and because the handle is captured in its recess unless downward pressure is applied at the correct location, it is difficult for children to remove the closure. The fact that the upper surface of the handle is flush with the upper surface of the cover conceals the existence of the handle and the proper method for releasing it. Thus, children are unlikely to discover the handle or discern the method for releasing it through inspection. A legend, which younger children cannot read, may be inscribed on the cover or container to instruct adults concerning removal of the closure.
Although the prior art closure described above appears to adequately protect against access by children, it is also relatively difficult for some adults to operate. Several features of the prior art closure create obstacles which are particularly difficult for people with poor eyesight, impaired coordination, limited strength, or other disabilities, to overcome. In particular, the retaining groove of the prior art closure cooperates so well with the inside lip of the container mouth that the large amount of force required to pull the closure from the container exceeds the capability of many product users. In addition, once the handle of the prior art closure has been released f rom its recess, it tends to remain in a position very close to the upper surf ace of the closure. It is difficult for some users to see the handle in that position. For other users, particularly those with limited manual dexterity or other coordination problems, it is difficult to move the handle into a position displaced from the top surface of the closure so that it may be gripped for use.